1. Field of the invention
The present invention relates to an open-close structure of a slide lid for a keyed instrument such as an electronic piano.
2. Description of Background Art
Heretofore it is known an open-close structure of a slide lid for a keyed instrument, for example, as disclosed in Japanese Laid-open Utility Model Publication No. 8390/1991. This slide lid is adapted to be slid between a closed position in which the lid is proximally drawn out of the main body of the musical instrument to cover the keyboard and an opened position in which the keyboard is exposed with the lid being pushed into the main body of the instrument. Inside plates of the arm members extended into the musical instrument are arranged at opposite sides of the keyboard. Each inside plates is provided, at its front exposed portion, with a decoration plate for supporting the slide lid in its closed position and for decorating the keyboard and, at its rear portion concealed in the musical instrument, with a rack as well as a guide groove for achieving smooth sliding motion of the lid. The rear end of the slide lid is provided with a pair of pinions which are arranged above said racks to mesh therewith and also provided with a supporting shaft for supporting the pinions of which opposite ends are adapted to be guided within said guide groove. That is, the supporting shaft is rotatably supported via a pair of holders at the rear end of the slide lid and each pinion is secured to the end of the supporting shaft with leaving a portion of the shaft which is received within the guide groove. Accordingly the slide lid can be slid uniformly in its right and left portions thereof due to its vertical motion guided by the guide grooves in the inside plates and due to the pinions rolling on the racks.
In the slide lid of the prior art, the oblique motion of the slide lid is prevented by the combination of said racks and pinions. However, since the weight of the slide lid is applied to the meshing portions of the racks and pinions during the opening and closing operation, the tooth tips of one of the rack or the pinion interfere with the tooth grooves of the other and clog each other, which causes a heavy load for opening and closing the lid as well as uncomfortable touch feeling generating rumble or noise. In addition, the use for a long period of time causes wear of the racks and pinions and looseness therebetween.